This invention relates to verification of telephone calls. Unwanted telephone calls are an issue with American phone service subscribers. Services like the National “Do Not Call” list provide some relief from marketing calls, but do govern many types of so called “cold calls.” Telephone services subscribers with Caller ID also have the ability to block calls from an unknown or withheld telephone number, but with little specificity.
Some telephone services subscribers have personal toll-free numbers that are managed by a password or set of passwords that can be distributed to those whom the subscriber allows to call. This prevents unwanted callers and charges on the toll-free number, but this system is tightly coupled as the password must be provided to the caller in advance and therefore the callers must be known to the subscriber.
Current technologies using caller ID, dial-tone and voice CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) provides for alternative authentication mechanisms where providers can challenge incoming callers and require valid responses before connecting a call or sending the caller to voice mail.
While there has been much work done in the field of screening and handling unwanted callers, these systems and methods provide limited functionality with respect to blocking unwanted telephone calls. In some cases, the system and methods described above may even block calls that are desired by the telephone services subscriber. Thus, there is a need for improved techniques for blocking unwanted telephone calls.